Composition for electrolytes for electrical etching



UNITED STATES PATENT OFFICE.

JOSEPH HENRY WEEKS, OF RUTLEDGE, PENNSYLVANIA, ASSIGNOR TO JACKSON SWEEKS; OF DELAWARE COUNTY, PENNSYLVANIA, AND RAYMOND M. WEEKS, OFPHILADELPHIA, PENNSYLVANIA, TRUSTEES.

COMPOSITION FOR ELECTBOLYTES FOR ELECTRICAL ETOHING.

No Drawing.

To all whom it may concern:

Be it known that I JOSEPH H. WnnKs, a citizen of the United tates,residing at Rutledge, in thecounty of Delaware, State of Pennsylvania,have invented certain new and useful Improvements in Composition forElectrolytes for Electrical Etching, of which the following is aspecification.

'My invention has for its object the production of an improvedelectrolyte for use in electricaletching of metals.

The general subject matter to which this invention relates is discussedin my prior applications, b'erial Numbers 88,362 108,232, and 119,548,filed respectively Apri l, 1916, July 8, 1916, and September 11 1916. Inthe first of said applications, I have disclosed a method, apparatus,and certain compositions for electrolytes intended to be used therein;in the second application, I have described and claimed a process andcomposition, and in the third application, I have described and claimedcertain improved apparatus. The electrolyte which I shall hereinafterset forth is adapted for use in the aforesaid processes, and with theaforesaid apparatus, although it is not necessarily limited thereto, andmay be employed in other connections, and for other metals or alloys ofmetals than those therein specifically described.

In the prior applications referred to, I have set forth a method ofetching plates in which a resistant image is produced on a plate,"either by means of ink or powder, which is well known in the art, or bymeans of a special gelatin albumen enamel of my own invention. The plateso prepared is suspended in a suitable bath or solution and connected soas to form the anode terminal of a circuit supplied with current ofsuitable voltage to produce the desired amperage or volume 0 currentflow per unit area of the anode. The cathode terminal, which is alsoimmersed in the bath or solution, may be of various types and of variousmaterials. In my application I have described carbon cathodes, and haveset forth means for keeping the surface of the late clean so that itshall be completely an uniformly exposed to the electrolytic action ofthe current, and for keeping the cathodes clean, and for preventinundercutting of the edges of the image hr lines on the plate.

Specification of Letters Patent.

Patented Dec. 14, 1920.

Application filed April 4, 1917. Serial No. 159,777.

The problems to be met are different from those presented in theelectro-plating art, because, in the latter, it is the deposition ofmetal which concerns the operator, and

which must be even and regular, as well as reasonably rapid; whereas, inthe present cases, it is the removal of the metal by the current into orthrough the solution, which must be properly regulated, and this to amuch greater degree of accuracy and uniformity than is necessary in theart of deposition.

In my experimental work, which has ex tended over a considerable period,and in the course of which the present invention and the othershereinbefore referred to have been produced, I have found that thecomposition of the electrolyte plays a very considerable part not onlyin the regulation of the action on the plate, but in the uniformity ofsuch action, and in maintaining said uniformity for any appreciableperiod of time.

Wit out going into detail at this time, into the chemical reactions orthe steps in transference of the metals, which take place with anyparticular composition, I may say generally that I have found it necessato provide a solution which shall have, rst, the proper conductivity;second, a capacity for absorbing and transferring the electricallydisplaced metal from the plate without soon coming saturated or clog ed;

third, no tendency to foul or coat or orm bubbles or spots upon theplate, which would impede the free passage ofthe current and thereby marthe engraying; fourth, no tendency, or a reduced tendency, to foul andform sludge upon the cathode surface in such manner that it cannot bereadily removed; and fifth, such elements and such a balance of forcesand properties that its efliciency will remain unimpared for a coninmost cases interchangeable with the invention set forth in my companionapplication Serial No. 159,776, filed April 4, 1917. The solutionclaimed in that case is a chlorid, alone or in combination with anoxalate, a chromium salt or a sulfate, with or without the addition orper-chlorid of iron or an acid, or both. The solution in the presentcase may have for its principal active element a sulfate in combinationwith a chlorid, but I shall not claim the same herein, as it is alreadyclaimed, although in inverse order, in the same companion application.

The class of metals with which this electrolyte is useful is very large,including all the metals specified in my prior applications abovereferred to, and many others. The

metals most commonly employed in the engraving art are copper, brass,steel, and zinc, and the plates are employed for printing, stamping, andfor other purposes. In addition to the engraving of steel printingplates both in relief and intaglio. the manufacture of steel dies andplates for stamping metals is, in itself, very important, and by myprocess, and with my.solutions, I can produce such dies and plates inmuch less time, and with much less expense, than where they are cut byhand according to the practice prior to this invention. Where the platesare to be employed for printing, my invention is specially important atthe present time, because of the scarcity of high grade paper, and thenecessity for having perfect printing plates in order to producesatisfactory results on the cheap grade of paper now commonly employed,because of such scarcity.

Electrolytes are prepared, for the greatest efiiciency and economy. forthe particular metals to be etched. Wherever practicable, a combinationis used in which the plate to be etched is kept clean without wiping.This is especially requisite in very delicate work, as frequent wipingwould tend to injure the material of the image. In coarse work, this isrelatively immaterial, and an electrolyte involving wiping of the-plate'may easily be used, and would be used where it is cheaper to prepare, orproduces a speedier action. The cleanliness of the cathode is nextpreferable, as involving less labor in keeping clean, or as renderingthat portion of my apparatus having movable brushes unnecessary. withaconsequent saving in power used thereby. For the reasons stated, some ofmy formulae do not give both a clean cathode and a clean anode.

The various use of sulfates, chlorids and chromates, with or withoutacids. is in some instances to secure anode or cathode plate cleanlinessor both, and to obtain electro lytes which shall form the best chemicalcombinations in themselves and with the anode, shall have the longestlife, and produce the smoothest etching, i. 6., to avoid rough grainyetching on either the sides of the lines or the bottom and further, tosecure a desirable speed which will admit of conr mercial etching of thevarious metals with practically the same electric current density. Thevalue of this last is obvious, particularly where one dynamo or batteryset is employed to supply current for the etching of different metals inseparate tanks without the emplo ment of reslstance.

An aci condition is desirable in all electrolytes to give stability tothe same and to increase the conductivity. If the constituent salts donot render the electrolyte acid or sufliciently acid for these purposes,an acid should be added. Some excellent electrolytes would promptlyseparate under electrolysis and promptly become useless were it not forthe addition of the acid. Even if this does not occur the life of theelectrolyte is shorter without acid and its conductivity less. Furtherin many cases the presence of an acid prevents precipitations in theelectrolyte or on the cathode or on the anode or performs two or all ofthese functions.

In some combinations where the ordinary acids do not keep the cathode orthe anode clean or prevent precipitations in the bath. this may in someinstances be partly or wholly accomplished by the addition of a chromiumsalt, or by what is generally termed chromic acid (usually potassiumdichromate solution acted upon by sulfuric acid), although the actionherein stated does not depend on the sulfuric acid in the chromic acidas that might independently be present in or added to the electrolyteunder the head of acids. The chromium salts are also employed on accountof their tendency to produce a smooth surface in the anode where it isfound that ordinarily the surface is rough. smoothness of the anodebeing usually a desirable feature.

Specifically stated, the solution to .be claimed herein consistsessentially of one or more of the sulfates of aluminum, ammonium,cadmium, calcium,chromium. cobalt, copper, iron, lithium, magnesium.manganese, nickel, potassium, tin, and zinc.

While the essence of the invention is the use of a suitable sulfate, Imay and do cinploy more than one, in combination, when required, but itis obvious that only those which will properly mix or combine can besimultaneously employed.

with the sulfates. I may combine a tartrate, an oxalate, or a chromiumsalt. or any combination thereof, with or without the addition of acid.I may also employ, an additional element, a small quantity of aperchlorid, such as the perchlorid of iron, containing an excess ofacid. This may be used in lieu of one or more of the foregoing sulfates,and in such case, no other acid is usually necessary. The principalfunction of the separate acid, if added, is to increase the conductivityand prevent decrease in current density and tends in most cases to keepthe face of the late clean and to prevent disintegration of thesolution.

As an example of a specific solution which I have found very useful forsteel and other metals, I may give the following:

Iron sulfate f 10;. Water 8 oz. Phosphoric acid (85%) 102.

The combination of a sulfate with i a chlorid are set forth in mycompanion application, and an example thereof isthe following:

Iron sulfate 10oz Sodium chlorid %oz. ater 8oz.

, As1an example of a solution in which an oxalate and an acidare"employed,.I may give the following:

Iron -sulfate 1 oz. lVater .8 oz.

Sat. sol. ammonium oxalate 2oz.

C. Pfsulfuric acid $02., (fluid) Iron sulfate 10 oz; \Vater 802. 7 Sat.sol. ammonium oxalate 2oz. Sodium chlorid; 1} oz. C. P. sulfuric acidioz.

, Sat. so]. potassium dichromate ioz.

As an example of a double sulfate, which is very effective, I may givethe followingi Iron sulfate .1oz., (by weight.)

dr chlorid of iron, with a slight excess of acid, may be addedseparately.

In the following claims, for the sake of brevity, a thiosulfate or asulfid are not specifically named, but their use is intended wherevernecessary. For example, in the case" of calcium sulfate, this wlllcombine mostreadily with sodium thin-sulfate; while with normalpotassium sulfate, it forms an insoluble mass. In the latter case, theaddition of a chlorid such as the chlorid of ammonium or sodium, andsome acid, will produce a perfectly clear solution.

The employment of a sulfid in some cases will produce results analogousto those produced by a sulfate.

It should be noted that wherever I mention one or more sulfates orchlorids, and it is proposed to employ, say, two or three of thoseindicated, it IS obviously meant that only those are contemplated whichwill properly combine or mix with others in the list. Double sulfates(also termed alums even where aluminum is not present), may be employedin place of combining the necessary single sulfates, and these willproduce equally good, and in fact, identical results that the two singlesulfates would if combined in proper molecular proportion. As a matterof fact, the solutions are then identical. Of cour'se,'with the use ofthe single salts, a preponderance of one on the other may be employed,at will.

Having thus described my invention, what I claim and desire to secure byLetters Patent of the United States is- 1. In electrolytic etching, ananode carrying a resistant image to be etched, in com bination with anelectrolyte comprising sulfate of iron with a mineral acid.

i 2. In electrolytic etching, an anode carrying a resistant image to beetched, in combiing a resistant image to be etched, in combi-- nationwith an electrolyte comprising one or more of the sulfates of aluminum,am-

monium, cadmium, calcium, chromium, copper, cobalt, iron, lithium,magnesium, manganese, nickel, potassium, sodium, tin, or

zinc, together with a chromium salt other than chromium sulfate.

4. In electrolytic etching, an anode carrying a resistant image to beetched, in combination with an electrolyte comprising one or more ofthesulphates of aluminum, ammonium, cadmium. calcium, chromium, copper,cobalt, iron, lithium, magnesium, manganese, nickel, potassium, sodium,tin, or zinc, together with an oxalate and achromium salt other thanchromium sulfate.

5. In electrolytic etching, an anode carrying a resistant image to beetched, in combination with an electrolyte comprising one or more of thesulfates of aluminum, ammonium, cadmium, calcium, chromium, copper,cobalt, iron, lithium, magnesium, mangaiiese, nickel, potassium, sodium,tin, or zinc, to which has been added an acid together with an oxalate.

6. In electrolytic etching, an anode carrying a resistant imageto beetched, in combination with an electrolytecomprising one or more of thesulfates of aluminum, ammonium, cadmium, calcium, chromium, copper,cobalt, iron, lithium, magnesium, mangancse, nickel, potassium, sodium,tin, or zinc, to which has been added an .acid together with a chromiumsalt other than chromium sulfate.

7. In electrolytic etching, an anode carrying a resistant image to beetched, in combination with an electrolyte comprising one or more of thesulfates of aluminum, ammonium, cadmium, calcium, chromium, cop per,cobalt, iron, lithium, magnesium, manganese, nickel, potassium, sodium,tin, or zinc, to which has been added an acid together with an oxalateand a chromium salt other than chromium sulfate.

S. A composition for electrolytes com prising one or more of thesulfates of aluminum, ammonium, cadmium, calcium, chromium, copper,cobalt, iron, lithium,

magnesium, manganese, nickel, potassium, t'in, zinc, or sodium, togetherwith a tartrate.

9. A composition for electrolytes comprising one or more of the sulfatesof aluminum, ammonium, cadmium, calcium, chromium, copper, cobalt, iron,lithium, magnesium, manganese, nickel, potassium, tin, zinc, or sodium,together with a tartrate and an oxalate.

10. A composition for electrolytes comprising one or more of'thesulfates of aluminum, ammonium, cadmium, chromium, copper, cobalt,iron, lithium, magnesium, manganese, tin, zinc, or sodium, together witha tarcalcium,

nickel, potassium trate, an oxalate, and a mineral acid other thansulfuric acid.

11. A composition for electrolytes comprising one or more of thesulfates of aluminum, ammonium, cadmium; calcium, chromium, copper,cobalt, iron, lithium, magnesium, manganese, nickel, otassium, tin,zinc, or sodium, together with a tartrate and a chromium salt.

' 12. A composition for electrolytes comprising one or more of thesulfates of aluminum, ammonium, cadmium, calcium, chromium, copper,cobalt, iron, lithium, magnesium, manganese, nickel, potassium, tin,zinc, or sodium, together with a tartrate, a chromium salt, and amineral acid other than sulfuric acid.

13. A composition for electrolytes comprising one or more of thesulfates of aluminum, ammonium, cadmium, calcium, chromium, copper,cobalt, iron, lithium, magnesium, manganese, nickel, potassium, tin,zinc, or sodium, together with a tar-' tr'ate'and a mineral acid otherthan sulfuric acid.

14, A composition for electrolytes comprising one or more ofthe'sulfates of aluminum, ammonium, cadmium, calcium, chromium, copper,magnesium, manganese, nickel, potassium, zinc, or sodium, together witha-tartrate, an oxalate, a chromium salt other than the sul fate, and amineral acid other than sulfuric acid. a

15. A composition for, electrolytes comprising one or more of thesulfates of alu- .minum, ammonium, cadmium, calcium, chromium, copper,scobalt, iron, lithium, magnesium. manganese, nickel, potassium, zinc,or sodium,together with a tartrate, an oxalate, and a chromium saltother than the sulfate. J

16. A composition for electrolytes comprising sulfate of iron and amineral acid other than sulfuric acid.

In testimony whereof I affix my signature.

liosnrn HENRY WEEKS.

cobalt, iron, lithium,-

